Quick bit of Background:
I had the SH 956 to start with then bust the Pick-ups, and needing a pick-up quickly and the fact I couldn't find replacements for the 956, I bought the SH 950.
I finally managed to get some replacement pick ups.
I mounted the both and compared.......
The Sh 950 is actually louder, but very attacky, and missing the real body, re my other thread of miking stuff up. It gets the vibrations only from the Bridge! - Needs EQing and Pre-amping pushing up the price from what you saved.
The SH 956 NFX has a pre amp and the nano flex pick ups sit under the bridge getting the vibrations from the sound board as well as the bridge. It is warm and lovely like a favourite old fully blanket.
Verdict??
The SH 956 NFX wins hands down, Without a
SHADOW of a doubt!

I can't believe I said that!